Atherogenic levels of low-density lipoprotein increase endocytotic activity in cultured human endothelial cells. |
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| Authors: | J. A. Holland K. A. Pritchard N. J. Rogers M. B. Stemerman |
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| Affiliation: | Department of Medicine, New York Medical College, Valhalla. |
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| Abstract: | Cultured human umbilical vein endothelial cells (EC) exposed to atherogenic low-density lipoprotein (LDL) levels for protracted periods demonstrated heightened endocytosis. Confluent EC were incubated with LDL 90 to 240 mg/dl cholesterol for 1 to 4 days and endocytosis was measured by 14C-sucrose uptake. Control EC and cells incubated with 90 mg/dl LDL cholesterol showed similar uptakes of 14C-sucrose during all measured time periods. In contrast, EC exposed to 240 mg/dl LDL cholesterol showed an increase in endocytosis beginning at 2 days, whereas 160 mg/dl LDL cholesterol promoted increased uptake by 4 days. The endocytotic activity of LDL-perturbed EC is reduced to levels seen in control cells by cytochalasin B, an actin polymerization inhibitor. This finding suggests a modulatory role for the cytoskeleton in endocytosis changes. Examination of LDL-perturbed EC cytoskeleton reveals structural remodeling resulting in a marked increase in stress fibers. Cytochalasin B exposure causes a loss of stress fibers with the formation of globular filamental aggregates. Such LDL-induced cellular functional changes may contribute mechanistically to endothelial dysfunction, which is widely held to be a major contributing factor in the pathogenesis of atherosclerosis. |
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